Old PC turns on then off. What is wrong?

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Nerdy Nerd

Nerdy Nerd

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Mar 19, 2016
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Ok, so I got a old computer from a family member. I turn on the desktop and all the fans run for about 1-2 seconds. Then it turns off. So I thought psu is the problem. I got my psu tester and it tested ok. I also put in another power supply to confirm that. Same problem happened. So I knew psu was good and put in the old psu since I know it is fine. Then I thought cpu is the problem. The cpu heatsink has 2 levers, one on each side. I tried to pull up and very direction but could not get it off. I was frustrated. So I just moved on and went to check ram. Now this is the interesting part. And yes I have tried other forums but there not like mine. There are 2 ram slots, one filled and the other is not. I took out the ram and noticed that all the fans stayed spinning. I thought, it is the ram the entire time. So I got a ram from another old desktop computer that I know works 100 percent. I installed it and heard two clicks like normal. Powered it on and same thing happened when I started diagnosing the computer, turns on then off. So I put the ram in the other slot and still, no good boot. Then I put the old one into the other slot so now both slots have ram. Turned on the computer and booted Windows like everything was fine. I thought ok it's fixed but I do not know why. Just for safe keepings, I tried to turn it back on right after that, turns on then off, so I am right back square one. Then I noticed something consistent. If I unplug and reply in the computer, it turns on just fine. Then I turn it off by power button and then tried turning it on again, no boot. Unplugged and plugged it in again and boots. Again, I turned it off by power button and tried to turn it on again by power button and no boot. Unplugged and plugged back in and boots. I think it is the switch maybe and not the ram. How do I test this theory without putting every component in another case? Wait a minute, when I press the power button, I get no boot but the fans do turn for 1-2 seconds like before then turn off. Might not be the switch because it does turn on, just no boot. In that case, I am just lost, nothing makes sense. The computer is all over the place it seems like. I need help, thanks in advance, what is wrong?
 
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To solve this problem try to isolate all the parts step by step procedure. No problem with the PSU because you check it now, so lets go to the MOBO, remove this part in the case and check this outside in the system case, connect the PSU, RAM, Processor and power up, then enter in the BIOS settings then change to default settings by pressing the keys assign in it like f9. Then setup again the BIOS like the time module, check also the voltage of the BIOS battery if its 3 volts. Now observe your mobo if it will not restart or it will off instantly, then go back here
 
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Have you perform this now

 
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Ok I tried changing the time and save changes. I booted the computer after trying a couple of times and it was not the time I saved it to. This means the cmos battery is bad right? I do not have a way of testing the voltage on the cmos battery. I do not know what you mean by default settings, I enter the bios and nothing there is default settings, you mean clear something or what? Computer still acts up.
 
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If the time module is not correct even you set it in a normal time, it is understood the cmos battery is longer normal voltage, try to replace it, Have you check in exit menu of the BIOS?There is restore in default settings there. What I need to know is after you save your BIOS the PSU will not instantly off?Or instantly go back to post. Can you tell me what is the POST message after you power on?Do not connect your HDD, because we diagnose the PSU and the mobo or the 3 main hardware
 
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Ok when I turned on the computer, the error is check date and time. When I did the default and saved, it went back to post and then said no operating system because my hard drive is not plugged in as you told me to do.
 
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Ok that is is there any other errors like memory test failed?So meaning to say there are also no post error like CMOS checksum error after you setup the BIOS main menu?If there are no post error rather than no os found and it will not hangup when pressing a keys it is understood that your mobo and PSU ram is normal. Check also the ram capacity displayed in BIOS main and in your RAM module capacity is the same. Then check also if the temperature of the south bridge IC and the northbridge IC is normal by touching it. I need to know if its all ok, try off again the computer using a paper clip, then power on again, observe if there are error you will observe or it will restart instantly or off.
 
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There is no other errors and it just said no operating system found. I checked to see if the bios reads the correct number for ram and it did. I checked both bridges and there fine. What do you mean by turn off your computer with a paper clip?
 
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Ok because I instructed you to remove the mobo outside of the system case, and I instruct you also to power up, you can use a flat screw rather to shorten the two pins of the power on to power-up the mobo with the PSU. Ok if this all ok as you said, meaning the problem is the HDD but lets try to isolate this also by testing outside in the system case, can you get out it in the bay and connect it in your mobo?lets see what happen. Be sure to check it in bios if it will detect normally.
 
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How do I know nothing will short out? What should I set the motherboard and psu on? It is getting late at where I live, so I will continue this tommrow. Thanks for your help by the way, thanks for being patient with me.
 
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Before you said to take the motherboard out so breadboarding it. Now you want me to have the motherboard in the case? As far as standoff screws, they are fine 100 percent sure. Ok cya tommrow, going to bed officially.
 
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Ok that's it, and connect the PSU to the mobo and power-up using flat screw, let see if it will post normally go to bios and observe if it will not suddently restart or off. If not connect your HDD only and observe if it will power up until to desktop. Then tell me what happen
 
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Ok if it is hard to you to find that power on pins, kindly assemble your mobo with the CPU and ram installed in the system case, be sure to properly inserted your mobo in the metal standoff of your system case, then do not use first your gpu, use only the built-in display port of your system unit, connect your power cord, monitor screen and keyboard then power up, enter to the bios if it will not hangs up, if not reboot your computer then connect your HDD and gpu, then power up again lets see if it will solve the problem.

 
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Ok so I put my motherboard and power supply back into the case. When I turned it on without the hdd, it did not stall at bios screen. It turned on without me pressing the power button. At the bios I noticed something, the power outage thing. I set it to off. After I saw that it did not kill on me, I turned the computer off and connected my hdd. I then connected my power cord to the back of the psu and it turned on and then killed on me. I then tried turning it on with the power button and it stayed on. When I pressed bios, it stalled for a while then finally entered. I noticed the power outage thing was not where I set it to. I knew the bios battery was bad from before but I think if the power outage thing is set some way, it will only start with the power cord plugged in. It changes because the bios or cmos battery is bad. Maybe the bios is the culprit or might be the hdd. What do you think? By the way, the gpu was connected always because I do not have another gpu. I know it is not the gpu because it was on from the start, point where I first installed the motherboard and psu back into the case.
 
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So make this clear and we will reduce the possibility of error, kindly replace that CMOS battery and setup your BIOS or restore to default settings after you change it. Be sure to replace the battery with same specs. Then lets talk again
 
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Ok I put in a good cmos battery or another wards, bios battery. It saved the changes for sure, so I know it is a good battery. First time I tried, turned on and then killed on me. Then I tried using the power button, killed on me. Went back to unplug and then I plugged it in again and I got it to stay on when I went to bios to set up everything. I had to try a couple more times before I was able to get the computer to stay on. I noticed another thing that was weird, well actually 2. First thing is when I was not in bios and just let it sit and run, it would make a loud sounds like ehhhhh. It is not like a loud fan or computer but sonething else. Second thing, right away when the computer turns on, the screen says disk error A. Yet, when I choose to move on and try loading the operating system, it would then check disk and I clicked to move on and see if it could load. It loaded, if it had an error, the hdd would not have let me boot into the windows os that I have installed on the hdd. I know the bios battery replacement fixed the saving issue and allowed me to boot into the os unlike before it said no operating system found. Anyways, computer is still acting up and killing at random. Really do not think a hard drive can cause the computer to start then kill at random. I also observed the power button made it a little difficult for me to turn on. Seems like when I press the button and it turns on, the button stays there and not come back a little. I have to Dinkle with it in order for it to go back. Might be the bottom too. Turns on and then stays there telling the computer to then turn off, maybe? Hdd? Other?
 
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Ok that drive a is the floppy drive in the bios settings disable it, now lets concentrate in the PSU and the mobo right?I suspect the mobo because it is hardly to trigger the power button this will also in the PSU because if the voltage out of PSU is inconsistent you can't easily power-up. It will only spin the cooler fan then it will off and start again.

Now to isolate this we need another PSU that have a good performance and same specs, use that in your mobo. But if the same results of the problem, we need to use another mobo with the same specs for your processor, RAM, and gpu, if this will results good your mobo is the bad.

But after you change you PSU then it will results good, replace that PSU. Then will go on of the HDD, if there are problems. But as you said you're HDD is normal right?
 
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Ok so I changed out the psu, it is a bran new psu that I got for free. Still acted up. When I was able to start the computer, it said date and time setting error. I just replaced the cmos battery yesterday. And for the disk a problem, there is nothing to disable that looks like that in the bios. I noticed something with the power button, when I pressed it and made it come back out right away, the computer stayed on the entire time every time. Three times in a row. Then once I just hit it and did nothing, it acted up. I think we maybe looking at power button problem and motherboard. I think motherboard because I changed the cmos battery and still gave me date and time error even though yesterday it never did after I replaced it. And before I posted this thread, I tried to get at the cpu and I could not get the heatsink off. It has 2 big levers on each side that I think just pull up instead of the normal pull to the right and then pull up. I tried every direction being gentle of course, and no go.
 
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